2017-04-20 14:07:24

by Colin King

Subject: [PATCH][-next] block, bfq: don't dereference bic before null checking it

From: Colin Ian King <[email protected]>

The call to bfq_check_ioprio_change will dereference bic, however,
the null check for bic is after this call. Move the the null
check on bic to before the call to avoid any potential null
pointer dereference issues.

Detected by CoverityScan, CID#1430138 ("Dereference before null check")

Signed-off-by: Colin Ian King <[email protected]>
---
block/bfq-iosched.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 6d14f18c0d45..bd8499ef157c 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4401,11 +4401,11 @@ static int bfq_get_rq_private(struct request_queue *q, struct request *rq,

spin_lock_irq(&bfqd->lock);

- bfq_check_ioprio_change(bic, bio);
-
if (!bic)
goto queue_fail;

+ bfq_check_ioprio_change(bic, bio);
+
bfq_bic_update_cgroup(bic, bio);

bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio, false, is_sync,
--
2.11.0

2017-04-20 14:20:13

by Jens Axboe

Subject: Re: [PATCH][-next] block, bfq: don't dereference bic before null checking it

On Thu, Apr 20 2017, Colin King wrote:
> From: Colin Ian King <[email protected]>
>
> The call to bfq_check_ioprio_change will dereference bic, however,
> the null check for bic is after this call. Move the the null
> check on bic to before the call to avoid any potential null
> pointer dereference issues.

Thanks, added.

--
Jens Axboe